Using higher order functions to apply a filter?

if user_filter:
   for each in something:
       if filter_condition_met:
          do_something(each)

else:
   for each in something:
       do_something(each)

Here I am repeating the entire code again which is against DRY principles.

for each in something:
    if user_filter:
       if not filter_condition_met:
          continue
    do_something(each)

Here I am doing the filter check for all items in the loop, while essentially it needs to be done just once.

Can I use higher order functions to check the filter condition once and generate a code that does the job? It looks like a filter and then transform operation. Can someone give some ideas?